Ground penetrating radar (GPR) systems are commonly used to detect objects, voids, cracks, or material interfaces beneath a surface. They may do so by emitting electromagnetic energy into the surface and measuring energy reflected back to the surface. The present invention relates to GPR systems and especially to the depth measurements performed by many GPR systems.
One example of such a GPR system is shown in U.S. Pat. No. 5,835,054 to Warhus et al., which describes a plurality of radar antennas directed at a surface that issue radar bursts and receive reflections from a range of depths under the surface. Timing of the bursts along with scanner signal selection is performed by a timing generator. Despite its advantages, Warhus describes the possibility of such GPR systems becoming overrun by the collected data. Warhus also describes how accuracy of such systems is dependent on how precisely the time-delay of echoes can be measured with each returned echo ideally being a scaled and time-shifted version of the transmitted pulse. Thus, simplified means for timing GPR systems may be desirable.
U.S. Patent Pub. No. 2015/0035693 to Hall et al. describes one effort to simplify the timing of GPR systems. Hall describes a signal generator transmitting one or more signals with one of the signals reflected off of a buried object back to the system and one of the signals transmitted along a variable length path. A correlator receives the signals and determines an offset between their arrival times. The variable length path may then be adjusted over a range to minimize the offset thus indicating a distance to the object. While this design offered significant improvements over that of Warhus in terms of simplicity, it also required time to adjust the variable length path. Thus, a simplified and faster GPR system may be desirable.